Video displays normally consist of a matrix of pixels, the intensity of each pixel determined by the magnitude of a video signal applied to the pixel. In many cases, the pixels are randomly addressable in a row by column format.
In previously developed systems, the video signal is sequentially connected to each pixel, typically comprising a phosphor element, by means of logic circuitry for addressing the pixels. The intensity of the addressed pixel is dependent upon the magnitude of a current through the phosphor. The current through the phosphor depends upon the potential between the video signal applied to the pixel and the voltage at a common cathode.
In the prior art, the video signal is applied to each pixel through logic circuitry, such as MOSFETs. Each MOSFET has a threshold potential V.sub.t which determines the conductance between the source and drain of the MOSFET for a given gate voltage. Hence, the brightness of each pixel is dependent not only upon the video signal applied to that pixel, but also upon the threshold voltage of the particular MOSFET connecting the video signal to the pixel. Since the threshold potentials of all the MOSFETs in the matrix vary from one another, the actual voltage present at the phosphor element depends upon the particular MOSFETs in the connecting circuitry. Therefore, a constant video signal will generate a non-uniform display. This has the effect of creating false images and obscuring genuine images.
Therefore, a need has arisen in the industry to provide, a video display in which the actual intensity of each pixel is unaffected by electrical parameters in the switching circuitry.